1. Field
The following description relates to a cache memory system and an operating method thereof.
2. Description of Related Art
In general, processing units such as a central processing unit (CPU) and a graphics processing unit (GPU) access and process commands and data stored in a large capacity external memory. Since processing speeds of most large capacity external memories are much slower than those of the processing units, a cache memory system is employed to improve an operation speed.
The cache memory system stores data that has been recently accessed by the processing unit. When the processing unit requests the same data again, the cache memory system accesses a high speed cache memory, instead of accessing an external memory, thereby improving a data transfer rate.
If the data requested by the processing unit is loaded on a data memory of the cache memory system (cache hit), the data is transferred to the processing unit. If the data requested by the processing unit does not exist (cache miss), the data is read out from the external memory. Also, the cache memory system erases any piece of cache data stored in the data memory, updates the erased cache data with the read data, and transfers the read data to the processing unit.
The cache memory system may be embodied in a set-associative cache memory using a set-associative mapping method and in a direct mapped cache memory using a direct mapping method, according to a mapping method. The set-associative cache memory has a plurality of ways. For the cache miss, the cache data corresponding to any one way is updated with new data read from the external memory according to a replacement status.